Indeterminacy in the WHO classification of tumors: an example of the histopathological diagnosis of brain tumors

摘要

The WHO classifications of tumors are the global standards of tumor diagnosis. In spite of the detailed descriptions of the histopathological features of tumors in the classifications, tumors may be difficult to diagnose or the diagnosis can be improper. One of the reasons is that the diagnostic criteria have indeterminacy. In this article, we clarify this indeterminacy and discuss the diagnostic problems associated with indeterminacy. Indeterminacy of the histopathological features is classified according to the following three points: specificity, constancy, and exclusiveness. We consider an oblique (ambiguous description), variable (not always present), or duplicative feature as an indeterminate feature. Under indeterminacy, pathologists make their diagnosis on the basis of their experience and heuristic reasoning, which can lead to improper diagnosis. Not only the histopathological features, but also the diagnostic criterion, will have indeterminacy, which may be the direct influence of the indeterminacy of the features. Also, it is possible for there to be too many combinations of findings that satisfy a criterion, preventing an exhaustive description. The diagnostic criteria of the WHO classification have indeterminacy. Users should therefore verify their diagnosis. Further efforts by WHO editors to improve the diagnostic criteria also are desirable.